Colour coding pneumatic tubing is one of the simplest and most effective ways to improve the safety, maintainability and clarity of a compressed air system. A consistent colour convention means that an engineer who has never worked on a particular machine can instantly understand the circuit layout without tracing every tube. This guide explains the most widely used colour conventions and how to apply them.
Why Colour Code Pneumatic Tubing?
On a busy machine with dozens of actuators, the pneumatic circuit can involve hundreds of tube connections. Without colour coding, fault-finding involves tracing tubes from component to component — a time-consuming and error-prone process. Colour coding allows engineers to identify supply, exhaust and signal tubes at a glance, dramatically reducing diagnostic and maintenance time.
Colour coding also reduces the risk of mis-wiring during machine build or after maintenance — particularly for bidirectional cylinder connections where swapping the A and B port tubes reverses the cylinder direction.
Common Colour Conventions
There is no single mandatory international standard for pneumatic tube colour coding, but several conventions are widely used across UK and European industry:
- Blue — main compressed air supply (the most common convention in UK industry)
- Black — exhaust or return to atmosphere
- Red — high-pressure supply, emergency or safety circuits
- Yellow — control signals or pilot air
- Green — secondary supply or clean/instrument air
- White or transparent — general purpose, vacuum, or food-grade applications
- Orange — cylinder advance (A port)
- Grey — cylinder retract (B port)
Some machine builders use their own colour standards which may differ from the above. The critical point is that your convention is consistent across all machines on site and documented in your engineering standards.
John Guest Colour Coding
John Guest manufactures pneumatic tubing in a wide range of colours specifically to support colour-coded circuit identification. Their Speedfit and Airline tube ranges are available in blue, black, red, yellow, green, white, orange, grey and clear. The consistent outer diameter tolerances of John Guest tube ensure reliable sealing in push-in fittings regardless of colour.
Applying Colour Coding in Practice
When implementing or upgrading a colour coding system:
- Document your convention — produce a one-page reference card specifying what each colour means in your facility and fix it to machine control panels.
- Apply consistently from the start — retrofitting colour codes to an existing unlabelled installation is much harder than building it in from the beginning.
- Use the same colours at both ends of a tube run — the supply end and the actuator end should use the same colour to allow tracing without following the physical tube.
- Supplement with labels at junctions — at manifold blocks and valve islands, supplement colour with numbered or letter-coded labels to identify individual circuits.
- Train all maintenance staff — colour coding only works if everyone on site uses and respects it.
Colour Coding for Safety Circuits
For emergency stop and safety shut-off circuits, consistent colour coding is particularly important. Reserve one colour — typically red — exclusively for safety-related air circuits and make this a hard rule in your engineering standards. Any red tube on a machine should be immediately recognisable as part of a safety function, making it clear that it must not be disconnected or modified without following the correct permit-to-work procedure.
Browse our range of John Guest pneumatic tubing in all standard colours to equip your next machine build or system upgrade.
Frequently Asked Questions
Is there a standard colour code for pneumatic tubing?
There is no single mandatory international standard for pneumatic tube colour coding. However, widely used conventions in UK industry include blue for main supply, black for exhaust, red for high-pressure or safety circuits, and yellow for control/pilot air. The most important requirement is that your chosen convention is consistent across all machines on site and documented in your engineering standards.
What colour is compressed air supply tubing?
Blue is the most common colour used for main compressed air supply tubing in UK and European industry. Some companies use black for supply and reserve blue for a different circuit u2014 this is why documenting and communicating your convention is essential.
Can I mix tube colours from different manufacturers in push-in fittings?
Yes, as long as the outer diameter (OD) is the same. Push-in fittings seal on the tube OD, not the colour. Use tubes with consistent OD tolerances (John Guest and other quality brands maintain tight OD tolerances) to ensure reliable sealing regardless of colour.
Browse our pneumatic components: